Causes

Pulmonary fibrosis scars and thickens the tissue around and between the air sacs (alveoli) in your lungs. This makes it more difficult for oxygen to pass into your bloodstream. The damage can be caused by many different things — including airborne toxins in the workplace, certain lung diseases, radiation directed to cancers in the lung or breast, and even some types of medical treatments.

Occupational and environmental factors

Long-term exposure to a number of toxins and pollutants can damage your lungs. These may include:

Silica dust

Asbestos fibers

Grain dust

Bird and animal droppings

Radiation treatments

Some people who receive radiation therapy for lung or breast cancer show signs of lung damage months or sometimes years after the initial treatment. The severity of the damage depends on:

How much of the lung was exposed to radiation

The total amount of radiation administered

Whether chemotherapy also was used

The presence of underlying lung disease

Medications

Many drugs can damage your lungs, especially:

Chemotherapy drugs. Drugs designed to kill cancer cells, such as methotrexate (Trexall) and cyclophosphamide (Cytoxan), can also damage lung tissue.

Medical conditions

Lung damage can also result from:

Tuberculosis

Pneumonia

Systemic lupus erythematosus

Rheumatoid arthritis

Sarcoidosis

Scleroderma

The list of substances and conditions that can lead to pulmonary fibrosis is long. Even so, in most cases, the cause is never found. Pulmonary fibrosis with no known cause is called idiopathic pulmonary fibrosis.

Researchers have several theories about what might trigger idiopathic pulmonary fibrosis, including viruses and exposure to tobacco smoke. And because one type of idiopathic pulmonary fibrosis runs in families, heredity also is thought to play a role.

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